1. Why are not stock prices predictable? ■例子:一种模型预测股票价格三天后将 从20元/股涨至23元/股 The forecast of a future price increase will lead instead to an immediate price Increase the stock price will immediately reflect the good news implicit in the model's forecast1. Why are not stock prices predictable? ◼ 例子：一种模型预测股票价格三天后将 从20元/股涨至23元/股 ◼ The forecast of a future price increase will lead instead to an immediate price increase ◼ the stock price will immediately reflect the good news implicit in the model’s forecast